In curable compositions for printed wiring boards such as solder resist, for the purpose of improving the physical strength of the coating films thereof, a method of adding a filler is commonly employed; however, in those compositions having such a low viscosity that makes the compositions applicable to an ink-jet method, a spin-coating method and the like, since precipitation of the filler occurs during long-term storage, there are problems of a change in the printability and deterioration of the coating film properties.